This invention relates to construction of structures on soils, as for example:
(A) base preparation of sub-grades for roads surfaced with concrete or asphalt pavements, gravel or other finishes;
(B) base preparation of sub-grades relating to airport runways and tarmacs surfaced with concrete or asphalt pavement;
(C) base preparation for concrete slab-on-grade buildings, walks, outside storage areas, etc. or the base preparation of sub-grades upon which any type of free standing building, equipment, etc. is to be placed no matter what finishing materials (gravel, sand, clay, etc.) will comprise the make-up of the balance of the sub-grade; and
(D) the base preparation and partial fill for the installation of water, storm and sanitary lines, and oil, natural gas and petroleum product lines.
In typical road construction, the terrain though which the road will go through is cleared, top soils removed and the preliminary grade cut out. The type of road that can then be constructed can vary but in colder climates it is not uncommon for a vapour barrier and rigid insulation to be placed on the preliminary grade and then the road bed brought up to its final grade by laying and compacting good clay material as per engineering requirements, and finished with a gravel, asphalt or concrete pavement surface. Similarly, base preparation for slab-on-grade structures requires excavation to remove organics and sub-grade preparation and in areas of permafrost and ice lensing, rigid Styrofoam™ sheets are laid to provide a thermal barrier and typically a vapour barrier is laid over the Styrofoam™ prior to concrete being poured over it.
The specifications for the construction of an airport runway or tarmac will in general be similar to that for the construction of a highway in terms of the make-up of the sub-grade. The strengths, materials tolerances, compaction requirements, etc. are more stringent but in general the process is similar. The terrain though which the runway will go through is cleared, top soils removed and the preliminary grade cut out. The type of runway to be constructed can vary but in colder climates it is not uncommon for a vapour barrier and rigid insulation to be placed on the preliminary grade and then the road bed brought up to its final grade by laying and compacting good clay material as per engineering requirements, and finished with a gravel, asphalt or concrete pavement surface.
For both roads and runways, the layer of vapour barrier (poly-ethylene sheet material) and the rigid insulation (Styrofoam™) have a number of inherent problems such as:
A) Typically the initial grade is relatively rough and uneven and can contain rocks, depressions and protruding sharp objects. This makes it difficult for a vapour barrier, if applied first, to retain its continuity when the balance of the road bed is loaded on top of it. The vapour barrier may tear and in the location of the tears, the vapour barrier will be undermined
B) The Styrofoam™ sheets are typically in 4 ft×8 ft pieces laid side-by-side in a staggered pattern but because the Styrofoam™ is laid in pieces, the crack between each of the sheets may allow moisture to penetrate from the top and where the vapour barrier is broken, from the bottom. Any break in the membrane will allow the transfer of water as well as heat. Further, the cracks and or breaks in the Styrofoam™ may trap water and during the winter months, and the freeze-thaw cycle may aggravate movement and settlement of the soils above the Styrofoam™.
C) Since the Styrofoam™ is rigid and since the initial grade of the road is uneven, the road bed and the Styrofoam™ do not meet. This may result in voids being left and when the balance of the road bed is laid on top of this layer of road bed, the Styrofoam™ is more readily broken. Further, any voids under the Styrofoam™ may entrap water and the freeze thaw cycle may consequently result in heaving and probable further break-up of the rigid Styrofoam™.
D) There is low structural strength or integrity in the vapour barrier and in the Styrofoam™ because of its piece-meal nature. Therefore, any settlement of the sub-grade below the Styrofoam™ will result in settlement throughout the road bed or sub-grade including the finished surface.
Buildings or other structures may be constructed slab-on-grade such as warehousing, residences, commercial and industrial buildings, or may be free standing structures that are placed directly on grade such as oil well-head housing and other protective shelters. Structures such as sidewalks, parking lots, patios, and the like may be situated on soils that may be undermined by the presence of sub-surface frozen soils such as permafrost and ice lenses as well as soils that are on muskeg, organics and very wet soils. In each of these structures, the lack of strength in the structural base may cause structural failure of the building or other structure.
An additional problem relating specifically to the oil and gas industry is the natural gas associated with oil production in areas where permafrost and ice lensing is commonplace. Natural gas flows up the drill hole and can accumulate in the well-head protective housing and pose an extremely dangerous condition.
In the servicing of municipal sub-divisions in cold climates, it is not uncommon in the placement of underground water, storm and sewer lines to excavate a trench, drop the lines in the trench, wrap the pipes in insulation and then back-fill. Typically the trench must be quite wide to facilitate workers and equipment in the trench to insulate the pipes. If the pipes are on soils that are on permafrost or where ice lensing is a reality there is the possibility that the lines will radiate sufficient heat to break down the permafrost or ice lens resulting in voiding occurring under the utilities lines and running the very real risk of the lines settling and eventually rupturing. A similar situation arises with under ground natural gas lines and under ground oil lines laid in soils where the presence of permafrost or ice lenses is a reality.
The present invention is directed to providing a reinforced foam base to assist in the stabilization of the sub-grade and minimize sub-grade degradation of the soils which will minimize building settlement and especially differential settlement of a building or other structure constructed on top of a reinforced foam base.